There has been known an air conditioner that heats air by using cooling water for an engine. When the air conditioner of this type introduces outside air, which is air outside a vehicle compartment, and blows the outside air into the vehicle compartment, the air-conditioner heats the outside air by using the cooling water. In this case, since the cooling water is deprived of heat by the outside air, the increase in the temperature of the cooling water is slow. As a result, a heating effect cannot be obtained quickly.
Therefore, a temperature increase control is known in which the engine is controlled such that the temperature of cooling water is further increased than usual in winter or such a period when inside-air temperature and outside-air temperature are low (refer to, for example, Patent Literature 1).